I've noticed this doing control builds on solsparc and win32. Here
is an example from a nightly build log found at:

http://koori.sfbay/java/re/j2se/1.5.0/nightly/logs/build-solaris-sparc.log

  :
for d in ./../src/share/classes ./../src/solaris/classes /BUILD_AREA/jdk1.5.0/control/build/solaris-sparc/gensrc; do (cd $d; /usr/bin/tar cf - `/usr/bin/find java/applet java/awt java/beans java/io java/lang java/math java/net java/nio java/rmi java/security java/sql java/text java/util com/sun/corba com/sun/image/codec/jpeg com/sun/imageio com/sun/java/swing com/sun/javadoc com/sun/jmx com/sun/naming com/sun/security/auth com/sun/security/jgss javax/accessibility javax/imageio javax/management javax/naming javax/print javax/rmi javax/security javax/sound javax/sql javax/swing javax/xml org/apache org/ietf org/omg org/w3c/dom org/xml/sax sunw -name SCCS -prune -o -name '*.java' \! -name '*-*' -print`) | (cd /BUILD_AREA/jdk1.5.0/control/build/solaris-sparc/j2sdk-image/src; /usr/bin/tar xf -); done
/usr/bin/find: cannot open org/apache: No such file or directory
/usr/bin/find: cannot open java/applet: No such file or directory
/usr/bin/find: cannot open java/awt: No such file or directory
/usr/bin/find: cannot open java/beans: No such file or directory
/usr/bin/find: cannot open java/math: No such file or directory
  :
  :

These error msgs do not appear to hurt anything.